In recent years, in the fields of production of medicines, gene therapy, regenerative medicine, immunotherapy or the like, it is required to culture a large amount of cells, tissues, microorganisms or the like efficiently in an artificial environment.
In such cell culture, in accordance with proliferation of cells, it is required to keep the density of cells in culture liquid in an appropriate range.
Specifically, if the density of cells in culture liquid becomes too high, it becomes impossible to supply sufficient oxygen or nutrition to each cell, thus leading to lowering in cell proliferation efficiency. Further, if the density of cells in culture liquid is too low, a sufficient proliferation efficiency cannot be obtained.
Therefore, in cell culture, in order to grasp the density of cells during culture, it is required to count the number of cells in culture liquid in a culture container, if necessary.
For example, Patent Document 1 discloses a counting device for counting the number of counting objects in liquid in a sealed container, which is provided with a table for mounting a container thereon and an adjustment member that adjusts at least part in a container, including a measurement-possible region, to a prescribed thickness.
This counting device is further provided with an imaging means for acquiring an image of counting objects in the container; a counting means for counting the number of the counting objects in an acquired image; and a driving means for driving the adjusting member that adjusts the thickness of at least part of the container to a prescribed thickness such that the number of the counting objects in the image will fall within a prescribed range if the number of the counting objects is not within a prescribed range as a result of measuring by means of the counting means.
Here, the principle of the method for counting the number of counting objects in Patent Document 1 will be explained with reference to FIG. 10. The principle of this counting method is applied to the counting device of one or more embodiments of the present invention.
FIG. 10 shows a state where cells in a culture container are directly observed by means of a microscope and the number of the cells is counted. FIG. 10A shows a state in which observation is conducted without adjusting the thickness T of the culture container. By using culture liquid having a specific gravity that is lower than that of cells, it becomes possible to allow cells to be sunk to the bottom of the culture container such that the cells can be those suited to microscopic observation. On the contrary, observation may be conducted by collecting cells to the upper part of the container by using culture liquid having a high specific gravity.
In the case of the state shown in FIG. 10A, as the number of cells in the culture container is increased, the cells gradually lie one on another when the cells are suspended and allowed to be settled. Therefore, by this method, the number of cells cannot be counted accurately when a large amount of cells is cultured.
Therefore, in the counting device of the Patent Document 1, in the case where accurate counting is impossible due to excessive number of cells, as shown in FIG. 10B, by reducing the thickness of the culture container to T′, the number of cells in a measurement range (observation range) is reduced, whereby the number of cells is adjusted to the number suited to counting.
As a result, if a large amount of cells is cultured in a culture container, by observing cells in a culture container directly, the number of cells can be counted without opening the culture system.
Further, when the number of cells in a culture container is small, and prediction of density of cells in an entire culture container is difficult, by increasing the thickness of a culture container, the number of cells in an observation range is increased, whereby the number of cells in the observation range can be adjusted to that suited to counting.